Integrated circuits (IC) generally include a variety of passive components. Capacitors are among some of the more common passive components that are widely used in ICs for various applications, e.g., mixed signal applications such as filters and analog-to-digital converters. Switched-capacitor circuits, for instance, are widely used in mixed-signal, analog-to-digital interfaces. Switched-capacitor circuits are typically used to perform a variety of functions, among others, sampling, filtering and digitization of signals.
Two capacitor structures that are widely used for such circuits are the metal-insulator-metal (MIM) capacitor and the metal-oxide-metal (MOM) capacitor. Generally, MIM capacitors include an insulator sandwiched between two layers of metals while MOM capacitors are composed of a large number of parallel “fingers” or electrodes formed on numerous metal layers.
In MIM capacitors, there is usually less parasitic capacitance as the top plate is shielded from ground by the bottom plate. As such, only minimal parasitic capacitance exists between the bottom plate and ground. However, MIM capacitors are generally more costly as they may require extra masks in the fabrication process.
Conversely, MOM capacitors can generally be easily fabricated at minimal to no extra cost on the available metal layers on a device. As such, as process technology shrinks, MOM capacitors have been widely used in analog applications due to the increase in capacitance density. However, MOM capacitors may have a higher parasitic capacitance compared to MIM capacitors. As a result of this, circuit operation may be adversely affected. For instance, analog-to-digital converter circuits that use MOM capacitors may suffer from gain error due to the higher parasitic capacitance.